A fire retardant panel door, often referred to as a “fire door,” is installed in homes, commercial buildings, and industrial plants for preventing the passage or spread of fire from one part of the building to another. In the interest of public safety, standards have been set by governmental agencies; and by municipal, county and state building code authorities and insurance companies for the installation and performance of fire doors. The standards require that the fire retardant doors be installed in wall openings and that they pass industry-wide acceptance tests.
Standard test methods for fire door assemblies, such as ASTM E-152, UL 10(b) or NFPA 252, measure the ability of a door assembly to remain in an opening during a fire to retard the passage of the fire and evaluate the fire resistant properties of the door. In conducting such tests, doors are mounted in an opening of a fire proof wall. One side of the door is exposed to a predetermined range of temperatures over a predetermined period of time, followed by the application of a high pressure hose stream that causes the door to erode and provides a thermal shock to the assembly. Doors are given a fire rating based on the duration of the heat exposure of 20 minutes, 30 minutes, 45 minutes, 60 minutes (one hour), 90 minutes (1½ hours) or 180 minutes (three hours). The door assembly receives the fire rating when it remains in the opening for the duration of the fire test and hose stream, within certain limitations of movement and without developing openings through the door either at the core or around the edge material.
A fire door must be made almost entirely of incombustible material. However, since a fire door is part of the interior or exterior of a personal living space or workspace, it must also be aesthetically pleasing. Usually, therefore, a core of incombustible material comprising the main structure of the fire door is overlaid with a thin wood veneer facing that provides the door with an attractive appearance. Fire door assemblies often fail, not because of the fire resistant properties of the fire door, but they fail because of inadequate placement of the fire resistance materials within the door, such that the fire door buckles. Additionally, the fire resistant blocking material of a core section of the fire door may need supplemental fire resistant materials strategically placed within the fire door to add to its fire door rating.
There remains a need for a reinforced fire retardant panel door and door frame which provides additional fire resistance using layers of intumescent and fire resistant materials in the fire retardant panel door and door frame in order to prevent buckling of the fire retardant panel door and door frame during a fire for at least 90 minutes. Further, the reinforced fire retardant panel door would include supplemental layers of fire resistant materials strategically embedded within the structural components of the fire retardant panel door.